Users are experiencing slow sync speed when downloading attachments.
Downloading the file, which is stored in Body field, costs much sync time.
Enable the On Demand model for documents by adding the Body field to the Exclude Field List on the VMOC record for the Document object. This prevents the Body field, which contains the actual file, from being included in the sync process. It saves sync time.
To add the Body field to the Exclude Field List, please open the VMOC record for Attachment and specify the field name: Body.